Microsoft has re-released a security bulletin to address errors in software updates related to the Microsoft Windows Media Services stack-based buffer overflow vulnerability.
Microsoft Windows Media Services 4.1 contains a vulnerability in the unicast streaming server that could allow an unauthenticated, remote attacker to execute arbitrary code.
The vulnerability is due to a failure to properly validate user-supplied input during the setup phase of a unicast Microsoft Media Streaming (MMS) session. An attacker who has the ability to contact the affected server and request a unicast stream could exploit the vulnerability. If successful, the attacker could execute arbitrary code with system-level privileges.
Functional code that exploits this vulnerability is available as a part of the Metasploit Framework module.
Microsoft has confirmed this vulnerability in a security bulletin and has released software updates.
Systems running Microsoft Windows Media Services 4.1 are affected. Windows Media Services 4.1 is only available with Windows 2000 Server.
An attacker could directly exploit this vulnerability by requesting a unicast MMS stream from an affected system and then submitting a malicious Transport Info packet as part of the stream setup negotiation. If successful, the attacker could execute arbitrary code with the privileges of the affected service. These privileges are sufficient to allow the attacker to completely compromise the affected system.
The Microsoft Windows 2000 platform was the only operating system on which the affected version of Windows Media Services was available. Due to the impending end of support by Microsoft, administrators are strongly encouraged to start planning a migration to a more current version of Microsoft Windows Server.
Previous software updates from Microsoft did not completely correct exploitation vectors that are related to this vulnerability. In response to these errors, Microsoft has released an updated security fix.
Microsoft has re-released a security bulletin at the following link: MS10-025
An unauthenticated, remote attacker could exploit this vulnerability to completely compromise the affected system.
This vulnerability exists because of a failure to properly handle user-supplied input by the Windows Media Unicast Service daemon, nsum.exe. When the affected service attempts to establish a new MMS session with a client, a negotiation sequence that involves the MMS TRANSPORT_INFO packet is used to determine the type of session that will be utilized.
An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious MMS TRANSPORT_INFO packet as a response during the negotiation sequence handshake. The processing of malformed packets by the affected service could result in a stack-based buffer overflow, corrupting memory. If successful, the attacker may gain the ability to execute arbitrary code with the Administrator privileges of the NetShowServices account that is used by the nsunicast service.
Administrators are advised to apply the appropriate updates.
Administrators may consider disabling unicast streaming until the appropriate updates can be applied.
Administrators may consider utilizing a host-based intrusion protection system to help mitigate the impact of successful exploitation.
Administrators are advised to monitor affected systems.
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
Version 4, April 22, 2010, 9:20 AM: Microsoft has re-released a security bulletin to address errors in software updates related to the Microsoft Windows Media Services stack-based buffer overflow vulnerability.
Version 3, April 20, 2010, 8:57 AM: Functional code that exploits the Microsoft Windows Media Services stack-based buffer overflow vulnerability is available.
Version 2, April 19, 2010, 8:40 AM: Additional technical information that describes the Microsoft Windows Media Services stack-based buffer overflow vulnerability is available.
Version 1, April 13, 2010, 2:05 PM: Microsoft Windows Media Services contains a vulnerability in the unicast streaming server that could allow an unauthenticated, remote attacker to execute arbitrary code. Updates are available.
The security vulnerability applies to the following combinations of products.
Windows Media Services
Advanced Server Base, SP1, SP2, SP3, SP4 | Server Base, SP1, SP2, SP3, SP4
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